Limit stop mechanism for potentiometers or the like



June 1952 w. J. OPOCENSKY 2,599,934

LIMIT STOP MECHANISM FOR POTENTIOMETERS OR THE LIKE Filed Oct. 31, 1950 I L:- IE- Snventor lV/LLA/PD d. 0poc4ws/(y Gttornegs Paten'ted June 10, 1952 LIMIT STOP MECHANISM FOR POTEN- TIOMETERS OR THE LIKE Willard John Opocensky, Glendale, Calif., as-

signor to Librascope, Incorporated, Glendale, Calif a corporation of California Application October 31, 1950, Serial No. 193,172

2 Claims.

The invention herein disclosed relates to vari able electrical resistance devices and more specifically to control means for the continuous resistance types of potentiometers or rheostats.

The main object of the invention isto provide means, operating in conjunction with the actuator for the movable element or slide travelling over a helical continuous resistance, for applying a positive stop to the actuator as the slide reaches its limit of movement at the opposite ends of the resistance helix.

Further objects are to improve the durability and efficiency and ease of adjustment of such devices while employing a simple combination of mechanical elements economical to manufacture.

A preferred form of the invention through which the above objects are achieved is hereinafter specifically described in connection with the accompanying enlarged scale drawing where,

Figure 1 is an end view of the device with its end cover omitted;

Figure 2 is a longitudinal section on line 22 of Figure 1 showing the portion of the device containing the slide actuator and stop mechanism;

Figure 3 is a plan view of the hunting tooth type stop mechanism operated by the actuator; and

Figure 4 is a similar view with the stop shown at the opposite limit of movement from that shown by Figure 3.

In the form disclosed, the device comprises the cylindrical housing ID, of any suitable nonconducting material, formed with a spiral internal grooved seat for reception of the continuous helical resistance element or wire H, which is retained in fixed position. One end of the housing I is provided with a bridge piece or cover |2 formed with a central aperture surrounded by an internally extending boss I3, while the opposite end (not shown) is preferably open. This aperture receives an elongated bearing sleeve extending into the casing l0 and formed with an external threaded end It and an enlargement l5 which seats within the boss IS. A clamping nut |6 on the end M of the sleeve serves to clamp the bearing sleeve in properly adjusted position in fixed relation to the housing It.

A rotor substantially co-extensive with the resistance helix has an actuating shaft |8 fixed centrally therein which is journaled in the elongated bearing sleeve and retained therein by a spring clip l9 seated in a groove in the shaft at the threaded end of the sleeve. The rotor I1 is formed with a slide groove 20 extending longitudinally from end to end of the rotor and slidably receiving a slide member 2|. This slide is provided with upstanding lugs 22 defining a transverse groove within which there is anchored, as at 23, a length of spring metal 24 terminating in the contact head 25. The lugs 22 serve to guide the slide along the resistance helix while the head 25 is held in contact therewith by its resilient support 24. A flexible lead wire 26 connects the support 24 of the contact. head with a contact plate 21 on the distal end of rotor forming one end of the resistancecircuit the other end of which resides in a post. or connector 28 leading to one end of the resistance helix The structure so far described is, in general, well known but is made a material part of the novel combination through which limitation of the travel of contact head 25 to the length of the resistance helix II is effected. This consists of a spur gear 3|] integral with or fixed on the elongated bearing sleeve within the housing In adjacent the boss I3 and a meshing spur gear 3| journaled on a pintle 32 seated in rotor gear 3| acting as a planet gear with respect to gear 30. The two meshed gears 30, 3| form a hunting tooth drive assembly carrying complemental stop members. Gear 30 has one more tooth than gear 4|. In this instance these gears have twenty and nineteen teeth, respectively. Under the meshed gears and in fixed relation thereto, gear 30 has two spaced stop projections or teeth 33 (Figures 3 and 4), while gear 3| carrles a complemental stop segment 34. The complemental stop members 33, 34 each extend slightly beyond the gear teeth and are so related. that the ends of segment 34 will come into abut ment with projections 33 at fixed periods in the opposite revolutions of the gears. In the present instance the relation of gear teeth in the respective gears will require ten revolutions of the rotor i1 and shaft iii to bring the complemental stop elements 33, 34 from the positions of Fi ure 3 to those of Figure 4. These ten revo1u tions will move slide H from one end of helix H to the other. Initial adjustment to put the slide on the end of the helix can be effected by releasing clamp nut Hi.

The foregoing combination of enclosed con tinuous helical resistance with positive stops applied to the actuator for the slide, through the medium of hunting tooth gearing, instead of to the slide itself presents obvious advantages. The comparatively fragile structure of the slide is relieved of the strain and wear which must result from stops applied directly thereto at each end of its path of travel. The stop impact, in the present invention, is received instead by the much more substantial actuator mechanism and the durability of the device as a whole is greatly improved. The disposition of gears on the sleeve and rotor is such that a compact and simple structure is obtained as well as an assembly which can readily be taken apart by mere removal of the clamp nut 16 thereby releasing the rotor and associated parts for removal from the housing.

What is claimed is:

l. The combination with a rheostat or the like having a cylindrical housing with an in ternal helical resistance winding, a fixed axial bearing sleeve extending within the housing and carried thereby, and a rotor within the housing carrying a contact slide for movement from end to end of the winding and having its actuating shaft journaled in the sleeve; of stop mechanism interposed between said sleeve and the rotor consisting of a hunting tooth gear set comprising a fixed spur gear on the sleeve and a complemental spur gear rotatably mounted on the rotor and moving therewith as a planet gear with respect to said fixed spur gear and complemental stop abutments on the respective gears, the tooth ratio between said gears being set to bring the abutments into locked relation as the slide reaches either end of the resistance winding.

2. The combination with a rheostat or the like having a cylindrical housing with an internal helical resistance winding, a fixed axial sleeve extending within the housing and carried thereby, and a rotor within the housing carrying a contact slide mounted for movement from end to end of the winding and having its actuating shaft journaled in the sleeve; of stop mechanism interposed between the sleeve and rotor consisting of complemental hunting tooth gears carried by the sleeve and rotor respectively and carrying stop abutments timed to reach locked relation after a predetermined number of rotations of the rotor in either direction.

WILLARD JOHN OPOCENSKY.

REFERENCES CITED UNITED STATES PATENTS Name Date Fox Aug. 22, 1950 Number 

